The good news is that if you are able to see the correct characters using SQL Developer, this indicates they are stored correctly in the database. The issue seems to be with how you are extracting the data or viewing the extracted file - pl provide details on both

set linesize 1500
set heading off
set pagesize 0
set feedback on
set verify off
set echo off
set timing off
set numwidth 13
set trimspool on
set colsep |
set serveroutput off
set termout off
ALTER SESSION SET nls_date_format='yyyymmdd';
spool international_char_test;
select * from brazil_test;
spool off;